In regard to the background of the invention it is to be stressed that polysaccharides are known to be biocompatible. Typical representatives in this connection are heparin, chitosan, alginate or hyaluronic acid. The latter have proven on the one hand to be highly body-compatible while on the other hand coatings of hyaluronic acid are hydrophilic and consequently the devices provided therewith can be well implanted.
Implants coated with polysaccharides in general and hyaluronic acid in particular and methods of coating them with hyaluronic acid are known from the state of the art in many different forms. Thus, U.S. Pat. No. 6,042,876, to Deem (Mar. 28, 2000), discloses a guide wire for implantation purposes, which is coated with such a polysaccharide such as hyaluronic acid or chondroitin sulfate.
Della Valle, in U.S. Pat. No. 4,957,744 (Sep. 18, 1990), teaches the crosslinking of esters of hyaluronic acid which are used for the most widely varying medical and cosmetic articles, as well as pharmaceutical compositions. The crosslinked esters result from the esterification of polyvalent alcohols with two or more carboxy groups of hyaluronic acid. Such crosslinked esters can be used in particular in the field of bioresorbable plastic materials for medical and surgical articles.
Finally, PCT publication WO 8802623 A1, by Guire at Bio-Metric Systems, Inc., relates to biomaterials with a biocompatible surface, wherein among a large number of starting materials and binding mechanisms there is disclosed inter alia the use of hyaluronic acid for the production of a biocompatible contact lens. This publication is related to U.S. Pat. Nos. 4,979,959 and 5,263,992.
Insofar as the above-mentioned publications concern coating methods for medical equipment and in particular stents, they suffer from the disadvantage that the polysaccharide layers produced do not achieve adequate levels of adhesive strength on the substrate surface.
Accordingly the object of the present invention is to provide a method of coating stents with a polysaccharide layer which enjoys improved adhesion on the substrate surface of the implant, and to afford correspondingly functionalized stents.